Field of the Invention
The present invention relates to an electron-beam exposure apparatus and, more particularly, to an electron-beam exposure apparatus for writing a pattern on a wafer or writing a pattern on a mask or reticle using a plurality of electron beams.
Known electron-beam exposure apparatuses are a point-beam type exposure apparatus which uses an electron beam having a spot cross section, a variable-rectangular beam type exposure apparatus which uses an electron beam having a variable-sized rectangular cross section, a stencil-mask type exposure apparatus which uses a stencil to shape the cross section of an electron beam into a desired shape, and the like, are known.
The point-beam type electron-beam exposure apparatus having a low throughput is only used for research and development. The variable-rectangular beam type electron-beam exposure apparatus has a throughput 10 or 100 times higher than that of the point-beam type apparatus, however, when it performs exposure with a fine and highly integrated pattern having a line width of about 0.1 .mu.m, the throughput becomes lower. On the other hand, the stencil-mask type electron-beam exposure apparatus uses a stencil mask having a plurality of repetitive pattern transmitting holes at positions corresponding to variable rectangular apertures. The stencil-mask type electron-beam exposure apparatus is advantageous in use of the repetitive pattern, however, when forming a semiconductor circuit requiring a number of transfer patterns which cannot be formed in one stencil mask, it is necessary to form a plurality of stencil masks and use them one by one. This takes mask exchange time, thus greatly lowers the throughput.
As an apparatus to solve these problems, a multi electron-beam type exposure apparatus is known. This apparatus deflects a plurality of electron beams to scan a sample surface based on coordinate values on a circuit design, and respectively turns on/off the electron beams in accordance with a pattern to be written, to write the pattern on the sample surface. As the multi electronbeam type exposure apparatus writes an arbitrary pattern without a stencil mask, the throughput can be improved.
FIG. 24A shows the schematic construction of the multi electron-beam exposure apparatus. In FIG. 24A, reference numerals 501a to 501c denote electron guns which turn on/off irradiation of electron beams; 502, a reduction electron optical system which projects a plurality of electron beams from the electron guns 501a to 501c in a reduced scale on a wafer 503; and 504, a deflector which deflects the electron beams projected on the wafer 503.
The plurality of electron beams from the electron guns 501a to 501c are deflected by the same deflection amount by the deflector 504. The respective electron beams are sequentially set at respective matrix positions on the wafer, by the deflecting operation by the deflector 504, in accordance with the matrix positions arranged at matrix intervals determined based on a minimum deflection width of the deflector 504, from respective beam reference positions as the reference positions. Then, the respective electron beams write patterns on elementary exposure regions different from each other.
FIGS. 24B to 24D show pattern exposure states where the electron beams from the electron guns 501a to 501c write patterns in the same matrix order on the respective elementary exposure fields. The respective electron beams simultaneously move in the respective elementary exposure regions, while the electron beams are set at matrix positions, (1,1) to (1,16), (2,1) to (2,16), (3,1) to (3,16), and (16,1) to (16,16). At positions of the patterns to be written (P1 to P3 in FIGS. 24B to 24D), the electron beams are turned on, so that the patterns are formed.
In the above-described multi electron-beam exposure apparatus, as the respective electron beams simultaneously write different patterns, the minimum deflection width of the deflector 504 is set from the minimum line width in the patterns to be written. As the minimum line width becomes finer, the minimum deflection width becomes shorter, accordingly, the number of electron-beam setting positions for exposure increases. As a result, the throughput is lowered.